Shredder

ABSTRACT

Apparatus for shredding sheet material including a housing having a front inlet and a rear outlet. A horizontal serrated abutment extends across the lower boundary of the front inlet through which sheet material is fed, as by a pinch conveyor. A horizontal arbor spaced rearward of the abutment rotates within the housing carrying cutting elements having pyramidal tips which trace paths of rotation that cause them to pass downward through the open regions between the serrations in the abutment, piercing the sheet material. Arcuate sections adjacent the tips of the cutting elements cause a ripping action to occur. The shredder operates at a much lower noise level than comparable equipment and provides uniform shredded materials that have interlocking edges.

United States Patent Johnson [451 Apr. 25, 1972 [s41 SHREDDER [22] Filed: Mar. 19,1970

[21] Appl.No.: 21,108

Primary Examiner-Granville Y. Custer, .lr. Attorney-Anderson, Luedeka, Fitch, Even & Tabin [5 7] ABSTRACT Apparatus for shredding sheet material including a housing having a front inlet and a rear outlet. A horizontal serrated abutment extends across the lower boundary of the front inlet through which sheet material is fed, as by a pinch conveyor. A horizontal arbor spaced rearward of the abutment rotates within the housing carrying cutting elements having pyramidal tips which trace paths of rotation that cause them to pass downward through the open regions between the serrations in the abutment, piercing the sheet material. Arcuate sections adjacent the tips of the cutting elements cause a ripping action to occur. The shredder operates at a much lower noise level than comparable equipment and provides uniform shredded materials that have interlocking edges.

9 Claims, 7 Drawing Figures FIGS FIGES l NVENTOQ @C/l/IFD Q (dam/50v SHREDDER This invention relates to shredders and more particularly to apparatus designed to shred sheet material, such as fiberboard.

Baling presses have been developed to compact and significantly reduce the volume of various types of waste material.

However, sheet material and particularly boxes made out of corrugated fiberboard are inherently difficult to compact. As a result, various types of shredding apparatus have been developed to reduce sheet material to a size which can be more effectively compressed into a bale and which can, if desired, be handled by pneumatic conveying equipment. The devices which have been developed for reducing the size of sheet material are often referred to as hoggers. Such hoggers generally operate at a fairly high noise level and produce a product that has been beaten and torn into nonuniform scraps. Improved versions of shredding apparatus are desired.

The principal object of the invention is to provide improved apparatus for shredding sheetmaterial. A further object of the invention is to provide improved apparatus for shredding sheet material which has a high capacity of throughput per hour and which has a low noise level. Another object of the invention is to provide apparatus for shredding sheet material which produces relatively uniform strips of the sheet material which strips have edges that interlock with one another and thereby facilitate the formation of a bale of material having excellent integrity.

These and other objects of the invention will be apparent from the following detailed description of apparatus embodying various features of the invention, especially when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view of shredding apparatus shown partially in section and illustrated in conjunction with a pinch conveyor unit at its inlet and a pneumatic conveying unit at its outlet;

FIG. 2 is an enlarged fragmentary perspective view looking downward into the shredding apparatus which is shown with its upper cover removed;

FIG. 3 is a fragmentary rear view of the apparatus shown looking generally along lines 3-3 of FIG. 1;

FIG. 4 is an enlarged perspective view of one of the individual cutting elements shown in FIGS. 1 through 3;

FIG. 5 is a side view of the cutting element shown in FIG. 4;

FIG. 6 is a section view taken along line 6-6 of FIG. 4; and

FIG. 7 is a fragmentary view of a strip of shredded sheet material that has passed through the shredding apparatus shown in FIGS. 1 through 3.

A shredder 11 is provided having a housing 13 wherein a horizontal arbor 15 is rotatively mounted. Strategically mounted on the arbor 15 are a plurality of generally radially or transversely extending cutting elements or blades 17. The housing 13 contains a front inlet opening 19 and a rear outlet opening 21. A front abutment 23 having a serrated rear edge defines the lower boundary of the front opening 19. The arbor I5 is spaced appropriately from the front abutment 23 so that the paths of rotation of the cutting elements 17 cause them to pass downward through the open regions between the serrations.

Sheet material to be shredded is fed into the front inlet 19 by a pinch conveyor 25 of standard construction. As the sheet material passes over the abutment 23, the downwardly rotating cutting elements 17 individually pierce the material and shred it into a plurality of generally parallel strips S having the general appearance shown in FIG. 7. These strips exhibit an inherent tendency to interlock with one another along their edges, and accordingly they provide an excellent material to be baled. This interlocked relationship of the strips provides an extremely secure bale which resists the tendency to breakdown that other baled materials exhibit when handled. Moreover, these strips are well adapted for automatic .handling by a pneumatic conveyor 27 located adjacent the rear outlet 21 of the shredder 11.

More specifically, the housing 13 includes a lower section 31, which is mounted on a suitable base 33, and an upper section 35 which is attached to the lower section by hinges 37 along the rear edge thereof. The inlet opening 19 is located between the upper and lower sections of the housing 13 whereas the rear outlet opening 21 is formed in the lower section 31 of the housing. The hinged attachment of the upper section 35 to the lower section 31 provides ready access for servicing the arbor 15 in its operative location within the housing 13. The upper edge of the front portion of the lower section 31 of the housing provides a flange 39 upon which the horizontal abutment 23 is suitably affixed, as by welding thereto. The front abutment 23 is located at a vertical level below that of the axis of the rotating arbor 15, as discussed in more detail hereinafter.

The arbor 15 includes a central shaft 41 which extends completely therethrough. The shaft 41 extends exterior of the housing 13 on both sides thereof through suitable openings provided therewithin at the junction between the upper and lower sections. The arbor shaft 41 is supported in a pair of split bushings 43 mounted on supports 45 that are attached to the base 33 at locations immediately exterior of both lateral faces of the housing 13. The arbor shaft 41, at its lefthand side as viewed in FIG. 2, has an extension 47 through which a connection is suitably made with a motor drive unit (not shown). Any suitable drive unit may be employed such as is well known in this art. The arbor 15 of the illustrated shredder 11 is desirably driven between about I and 200 rpm, well below the speed of conventional hoggers.

The arbor IS, in addition to the central shaft 41, includes a plurality of spaced discs 49 to which the individual cutting elements 17 are mounted. Although various mechanical con structions may be used for the arbor, in the illustrated embodiment, the spaced discs 49 are in the form of annular rings which are suitably affixed, as by welding, to the exterior surface of a tube 51 of circular cross section. The tube 51 is mounted coaxially about the arbor central shaft 41 by a pair of spacers 53 at each end thereof. Each of the cutting elements 17 is suitably mounted to one of the discs 49. In the illustrated embodiment, each cutting element 17 (FIG. 4) includes a pair of holes 55 which align with similarly spaced holes drilled in thediscs 49 and thus facilitates attachment via nuts and bolts 57.

Each of the cutting elements 17 is formed to extend at an angle to the discs 49 to which they are attached so that the cutting portions of the elements are not aligned perpendicular to the axis of the arbor 15 but are disposed at an angle A to the perpendicular (see FIGS. 2 and 5). Disposition at such an angle is considered important to assure that the strips 5 which are created have edges which interlock with one another when compressed into a bale. This angle A should be at least about 25 and not greater than about 45. In the illustrated embodiment, the angle A measures about 30.

As best seen perhaps in FIGS. 4 and 5, the cutting elements 17 each have a flat base portion 59 wherein the holes 55 are provided through which the bolts 57 pass that mount the elements to the arbor discs 49. A blade portion 61 of the cutting elements 17 is offset from the plane of the base portion 59 by the angle A, which in the illustrated version is about 30. The cutting element 17 is generally symmetrical, being formed with a pyramidal tip 63 at each end of the blade portion 61. Although the trailing pyramidal tip of each blade is not functional in its assembled condition on the shredder 11, the symmetry of the cutting elements 17 permits them to be mounted on either side ofa mounting disc (see FIG. 3).

The cutting elements 17 may be formed in any suitable manner and are preferably cast from metal. The front and both sides of the blade portion 61 of the cutting elements 17 is beveled to produce the three-sided pyramidal tips 63 at the free ends of the cutting elements and to also provide a blade edge 65 which extends rearward from the pyramidal tip on both lateral sides.

As best seen in FIG. 4, the blade portion 61 is reduced in width just rearward of the pyramidal tips 63 to provide an arcuate or hook section 67 of the edge. The provision of such an arcuate section 67 at this location has been found to facilitate the creation of a tearing action in the sheet material after the initial piercing by the tip 63, which occurs at the location of the serrated abutment 23. As explained in more detail hereinafter, the tearing action occurs because the pinch conveyor 25 is used to limit the speed of travel of the sheet material past the abutment 23 while the arbor 15 is driven at a speed so that the cutting elements 17 are moving several times as fast as the sheet material during the short period of their engagement. It is found that the provision of the arcuate sections 67 enables the cutting element 17 to achieve firm contact with the sheet material which instigates the ripping or tearing action.

It has also been found that the location of the serrated abutment 23 slightly below the vertical level of the axis of the arbor l facilitates achievement of the desired tearing action. Preferably, the relative locations are such that a line through the arbor axis of rotation and the rear points on the serrations makes an angle between about 1 and about 3 with the horizontal. As a result of this disposition, the cutting elements are not only moving downward when initial contact is made with the sheet but are beginning to move back toward the vertical plane of the axis ofthe arbor. This horizontal component of movement plus the arcuate section 67 promotes the uniform occurrence ofthe desired tearing action.

As best seen in FIG. 2, each of the mounting discs 49 is aligned with rear tips of one of the serrations of the serrated abutment 23, and the cutting elements 17 are mounted alternately on one side and then the other of each mounting disc. In the illustrated embodiment, the arbor 15 includes eight spaced mounting discs 49, and accordingly there are eight serrations, one aligned with each disc. Through each of the seven open regions between these eight serrations, pass cutting elements 17 mounted on two adjacent discs, the paths of which overlap and intersect one another. For example, in each one of these seven central open regions, there will be four cutting elements 17 that will rotate therethrough two, spaced 180 apart, on the facing sides of each adjacent pair of mounting discs 49.

In order to get the desired cutting and tearing action that produces the strip configuration with the edge pattern shown in FIG. 7, it is important that these cutting elements 17 be disposed at an angle from the planes normal to the axis of revolution and with a relative spacing so that overlapping occurs (as best seen in the two elements 17 shown at the lefthand side of FIG. 3.) If a sheet of corrugated fiberboard, for example, is fed into the shredder 11, which sheet is substantially as wide as the arbor, this sheet will be cut into strips, the central eight strips of which will resemble the strip 5 depicted in FIG. 7, The two outermost strips will have only one lateral edge out with the edge pattern shown.

These eight strips 5, which are created from such a full width sheet passing through the shredder 11, have a configuration somewhat resembling the outline of an evergreen tree. The solid central or trunk portion of the strip 5 is that portion of the sheet which was generally aligned with the mounting disc 49 during its passage through the shredder. Each of the penetrations which creates one of the branches of the evergreen configuration is caused by the passage of one of the cutting elements 17 through the sheet material. The angle at which each of the branches extends downward from the central trunk portion results from the angle A at which the blade edges 65 of the cutting elements are disposed to the planes normal to the rotational axis ofthe arbor.

The spacing between the branches is determined by the speed at which the pinch conveyor 25 feeds the sheet material into the shredder l1 and by the rate of speed at which the arbor is driven. This point is discussed further hereinafter. Although the two-dimensional drawing shown in FIG. 7 depicts the strips S as being generally flat, it should be understood that sheet material which once occupied the open regions between adjacent branches has in general not been removed from the strips but is bent down and often folded under the branches which appear in FIG. 7. The ripping action creates a raw or ragged edge on the depending portions of the corrugated fiberboard sheets which underlie the branches. As previously indicated, the provision of this edge pattern with the extending branches produces strips S which interlock with one another to provide a very secure bale. Moreover, the dissolution of the corrugated material in a subsequent pulping operating, to which much shredded corrugated fiberboard material is eventually routed, is facilitated by the ragged edges.

To attempt to maintain the passage of the strips 5 through the shredder 11 in a generally parallel fashion, five grates or dividers 71 are mounted in the lower section 31 of the housing. The dividers 71 are plates which, as best seen in FIG. 3, are individually aligned with one of the mounting discs 49 and extend downward from the underside of the serrated abutment 23. The dividers 71 thus partition the region below the arbor 15 and abutment 23, where the cutting and shredding occurs, into six compartments. This arrangement has been found to be quite effective in avoiding tangling of one strip S with another and with the cutting blades 17. Should the strips S become wrapped around the arbor 15 through entanglement with the cutting elements 17, shutdown of the shredder 11 is required in order to manually remove such a blockage.

As best seen in FIGS. [-2, the shredder 11 also includes the provision of eight stripper fingers 73 which are mounted on the rear wall of the lower section 31 of the housing at a location just above the outlet opening 21. The eight stripper fingers 73 are also each individually aligned with one of the mounting discs 49 of the arbor 15. The stripper fingers 73 have been found to be extremely effective in preventing the strips S from being carried upward with the cutting elements 17 over the top of the rotating arbor 15 which might result in strips being wrapped around the arbor as just discussed. The presence of the stripper fingers 73 assures that the strips S are deflected into the region of the rear outlet 21 where the suction action of the pneumatic conveyor assures the strips leave from the shredder 11 at the desired exit.

Overall, the cutting elements 17 create a definite pulling action upon the sheet which, if unrestrained, would be pulled directly through the shredder 11, In order to achieve the desired tearing action following the initial piercing ofthe sheet material, it is necessary to restrain the sheet at the point of infeed, as by regulating its linear speed into the shredder 11. In the illustrated embodiment, such regulation is accomplished by the pinch conveyor 25, which also has the advantage of being designed to compress corrugated boxes into flat form. For example, the pinch conveyor 25 may be set to feed the sheet material into the shredder 11 at a rate of about 45 feet per minute. Using a shredder 11 having an arbor 15 which measures about 24 inches diametrically from cutting tip 63 to cutting tip 63, the arbor 15 is preferably driven-at about to rpm. This operative combination creates an effective lineal speed of the cutting elements that is about three to four times the speed of the sheet material and thus provides the desired ripping action after the initial penetration of the pyramidal tip. It also produces satisfactory spacing between branches in the resulting strip S, generally as is shown in FIG. 7.

As is apparent from FIG. 2, the location of the cutting elements 17 on the mounting rings 49 is staggered 'so that preferably there is contact being made only between one pyramidal tip 63 and the sheet material at one time. The mounting pattern is generally that of a spiral about the axis of the arbor 15. Obviously, if the shredder 11 is scaled up in size to accommodate a sheet twice as wide, thus necessitating about twice as many cutting elements 17, it might be desirable to permit two cutting elements to hit at the same time rather than attempt to divide the available 360 into still smaller increments.

In summary, the shredder 11 of the illustrated design, operating on the aforementioned principles, has been found to be extremely efficient in operation, having a high capacity for shredding sheet material relative to the amount of space which it occupies in a plant. For example, about 4 tons of corrugated fiberboard per hour can be shredded in an apparatus about 50 inches wide. The manner in which the shredder 11 operates, namely one of piercing followed by ripping, creates a substantially lower noise level than hoggers which have been previously employed to reduce waste sheet material to a size suitable for baling. This substantial reduction in noise level results from being able to operate the arbor at 200 rpm or less while conventional hoggers operate between about 600 to 1,200 rpm. Efficient operation at such a significantly slower rpm. is made possible because of the shape of the cutting elements that accomplish the piercing and ripping action. Inasmuch as the population is becoming more and more noise-conscious, this is considered to be an important advantage of the apparatus. Perhaps most importantly is the ultimate uniform configuration, referred to as the evergreen outline, of the strips which result from the passage of sheet material through the shredder. The edge pattern not only facilitates interlocking when this material is ultimately baled by a mechanical baler, but the raw edges which are created for a considerable linear distance along the outline of the branches provide the shredded material with excellent dispersion characteristics for ultimate disposal in a pulping operation.

Moreover, the uniform creation of strips of fairly regular sizes is a considerable advance over prior art devices which create a significant fraction of small pieces.

Various modifications which would fall within the spirit of the invention as viewed by one skilled in this art are considered as coming within the scope of the invention that is defined by the appended claims. Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. Apparatus for shredding sheet material which apparatus comprises a housing having a front inlet and a rear outlet, a stationary horizontal abutment extending generally across the front portion of said housing and defining the lower boundary of said front inlet through which the sheet material is fed, a horizontal arbor extending parallel to said abutment and spaced rearward thereof, means mounting said arbor for rotation within said housing, a plurality of cutting elements formed with pyramidal leading tips mounted generally transversely on said arbor, and means for rotating said arbor to cause cutting elements to trace paths of rotation thereabout, said front abutment having a serrated rear edge and said cutting elements being proportioned and located so that the paths of rotation thereof cause them to pass downward through the open regions between the serrations in said abutment so that said pyramidal tips initially pierce the sheet material at about the location of said stationary abutment.

2. Apparatus in accordance with claim I wherein said cutting elements have arcuate blade edges adjacent said pyramidal tips which produce a ripping action in the sheet material after the initial piercing action.

3. Apparatus in accordance with claim 1 wherein said axis of rotation of said arbor is positioned above the level of said stationary abutment so that a line drawn through said axis of rotation and the rear points on said serrations makes an angle of between about 1 and about 3 with the horizontal.

4. Apparatus for shredding sheet material which apparatus comprises a housing having a front inlet and a rear outlet, a stationary horizontal abutment extending generally across the front portion of said housing and defining the lower boundary of said front inlet through which the sheet material is fed, a horizontal arbor extending parallel to said abutment and spaced rearward thereof, means mounting said arbor for rotation within said housing, a plurality of cutting elements having free end portions formed with pyramidal leading tips mounted generally transversely on said arbor, and means for rotating said arbor to cause said cutting elements to trace paths of rotation thereabout, said front abutment having a serrated rear edge and said cutting elements being proportioned and located on said arbor with said free end portions being disposed at an angle of at least about 30 with the plane perpendicular to the axis of rotation so that the paths of rotation of said pyramidal tips cause them to pass downward through the open regions between the serrations in said abutment with said pyramidal tips initially piercing the sheet material at about the location of said stationary abutment.

5. Apparatus in accordance with claim 4 wherein said plurality of cutting elements are mounted at spaced locations longitudinally of said arbor with cutting elements at adjacent mounting locations extending inwardly into the region between said spaced locations so that cutting elements from two adjacent mounting locations rotate through said same region in said serrated stationary abutment.

6. Apparatus in accordance with claim 5 wherein said spacing between said adjacent locations is such that there is overlapping between the paths of rotation of said angularly disposed cutting elements mounted at adjacent locations.

7. Apparatus in accordance with claim 6 wherein said arbor includes a plurality of spaced, parallel mounting discs disposed perpendicular to said axis of rotation, said cutting elements being mounted along the peripheries of said discs, and wherein vertical divider places are provided in said housing which are aligned with various of said discs and are located therebelow and extending rearward from said serrated abutment.

8. Apparatus in accordance with claim 7 wherein said outlet is located in a rear wall of said housing and extends upward to a vertical level about that of said axis of rotation, and wherein a plurality of stripper fingers are mounted on said rear wall at locations above said outlet, said fingers being aligned with and extending toward said discs.

9. Apparatus in accordance with claim 1 wherein means is provided for feeding sheet material over said abutment at a regulated linear speed which is substantially less than the speed at which said cutting elements are moved. 

1. Apparatus for shredding sheet material which apparatus comprises a housing having a front inlet and a rear outlet, a stationary horizontal abutment extending generally across the front portion of said housing and defining the lower boundary of said front inlet through which the sheet material is fed, a horizontal arbor extending parallel to said abutment and spaced rearward thereof, means mounting said arbor for rotation within said housing, a plurality of cutting elements formed with pyramidal leading tips mounted generally transversely on said arbor, and means for rotating said arbor to cause cutting elements to trace paths of rotation thereabout, said front abutment having a serrated rear edge and said cutting elements being proportioned and located so that the paths of rotation thereof cause them to pass downward through the open regions between the serrations in said abutment so that said pyramidal tips initially pierce the sheet material at about the location of said stationary abutment.
 2. Apparatus in accordance with claim 1 wherein said cutting elements have arcuate blade edges adjacent said pyramidal tips which produce a ripping action in the sheet material after the initial piercing action.
 3. Apparatus in accordance with claim 1 wherein said axis of rotation of said arbor is positioned above the level of said stationary abutment so that a line drawn through said axis of rotation and the rear points on said serrations makes an angle of between about 1* and about 3* with the horizontal.
 4. Apparatus for shredding sheet material which apparatus comprises a housing having a front inlet and a rear outlet, a stationary horizontal abutment extending generally across the front portion of said housing and defining the lower boundary of said front inlet through which the sheet material is fed, a horizontal arbor extending parallel to said abutment and spaced rearward thereof, means mounting said arbor for rotation within said housing, a plurality of cutting elements having free end portions formed with pyramidal leading tips mounted generally transversely on said arbor, and means for rotating said arbor to cause said cutting elements to trace paths of rotation thereabout, said front abutment having a serrated rear edge and said cutting elements being proportioned and located on said arbor with said free end portions being disposed at an angle of at least about 30* with the plane perpendicular to the axis of rotation so that the paths of rotation of said pyramidal tips cause them to pass downward through the open regions between the serrations in said abutment with said pyramidal tips initially piercing the sheet material at about the location of said stationary abutment.
 5. Apparatus in accordance with claim 4 wherein said plurality of cutting elements are mounted at spaced locations longitudinally of said arbor with cutting elements at adjacent mounting locations extending inwardly into the region between said spaced locations so that cutting elements from two adjacent mounting locations rotate through said same region in said serrated stationary abutment.
 6. Apparatus in accordance with claim 5 wherein said spacing between said adjacent locations is such that there is overlapping between the paths of rotation of said angularly disposed cutting elements mounted at adjacent locations.
 7. Apparatus in accordance with claim 6 wherein said arbor includes a plurality of spaced, parallel mounting discs disposed perpendicular to said axis of rotation, said cutting elements being mounted along the peripheries of said discs, and wherein vertical divider places are provided in said housing wHich are aligned with various of said discs and are located therebelow and extending rearward from said serrated abutment.
 8. Apparatus in accordance with claim 7 wherein said outlet is located in a rear wall of said housing and extends upward to a vertical level about that of said axis of rotation, and wherein a plurality of stripper fingers are mounted on said rear wall at locations above said outlet, said fingers being aligned with and extending toward said discs.
 9. Apparatus in accordance with claim 1 wherein means is provided for feeding sheet material over said abutment at a regulated linear speed which is substantially less than the speed at which said cutting elements are moved. 